It would cost over $1 billion (a Gigabuck)
to develop this Linux distribution by conventional proprietary means
in the U.S. (in year 2000 U.S. dollars).

It includes over 30 million physical source lines of code (SLOC).

It would have required about 8,000 person-years of
development time, as determined using the widely-used basic COCOMO model.

Red Hat Linux 7.1 represents over a 60% increase in
size, effort, and traditional development costs over Red Hat Linux 6.2
(which was released about one year earlier).

Many other interesting statistics emerge; here are a few:

The largest components (in order) were the
Linux kernel (including device drivers), Mozilla
(Netscape's open source web system including a web browser,
email client, and HTML editor),
the X window system (the infrastructure for the graphical user interface),
gcc (a compilation system),
gdb (for debugging),
basic binary tools,
emacs (a text editor and far more),
LAPACK (a large Fortran library for numerical linear algebra),
the Gimp (a bitmapped graphics editor), and
MySQL (a relational database system).
Note that some projects (in particular KDE and GNOME) are in aggregate
large enough to be one of the largest components, but because they are
developed and distributed as a large number of smaller components,
their totals don't appear in the list of largest components.

The predominant software license is the GNU GPL.
Slightly over half of the software is simply licensed using the GPL,
and the software packages using the copylefting licenses (the GPL and LGPL),
at least in part or as an alternative, accounted for 63% of the code.
In all ways, the copylefting licenses (GPL and LGPL) are the dominant licenses
in this Linux distribution.
In contrast, only 0.2% of the software is public domain.

When referring to this information, please refer to the URL
http://www.dwheeler.com/sloc.
This is not a legal requirement; of course you are always allowed
to deep link to anything you want to!
This is just a friendly recommendation, since
some of the other URLs may change, and I may add more measurements later.

Others have been inspired by my paper
More than a Gigabuck: Estimating GNU/Linux's Size to
do more analysis, which is great:

One group did an analysis of the Debian GNU/Linux distribution, using my tool
sloccount.
You can see their very interesting paper
Counting Potatoes: The size of Debian 2.2 at
http://people.debian.org/~jgb/debian-counting,
or you can see an older version of it in
Upgrade.
They found that Debian 2.2 includes more than 55 million physical SLOC, and
would have cost nearly $1.9 billion USD using over 14,000 person-years
to develop using traditional proprietary techniques.

Comparitive numbers are hard to find.
Gary McGraw (of Cigital) has searched public information to find
Windows SLOC size.
According to his sources, Windows NT 5.0 (in 2000) was 20M SLOC,
Windows 2000 (in 2001) was 35M SLOC, and Windows XP (in 2002) was 40M SLOC.
(This information is from his briefing
Building Secure Software: How to avoid security problems
the right way).
Another source claims that
Windows NT's original release (in 1992) contained 4 million lines,
while NT 4.0 (released in 1996) expanded to 16.5 million lines.
(
"Crash-Proof Computing" by Tom R. Halfhill,
Byte, April 1998).
"This Car Runs on Code" by Robert N. Charette (IEEE Spectrum, 2009-02-01)
stated that "It takes dozens of microprocessors running 100 million lines
of code to get a premium car out of the driveway, and this software is
only going to get more complex".
"Codebases" at Information is Beautiful creates
an interesting visualization of various lines-of-code numbers.
Lines of code is a Google doc
spreadsheet of various sizes, with URLs to the information sources.

Palle Pedersen
done a rough-order-of-magnitude analysis of all
Free-libre / open source software,
starting with some extremely simplifying assumptions.
"Assuming an average open source project is 35,000 lines
of code and the average cost of a software developer is
$30/hour (~$60,000/year), a simple COCOMO II calculator tells us
that the average open source project costs $630,000 to develop.
This cost translates into $18 per line of code.
Extrapolating that to 1.7 billion lines of code gives
us an estimated value of $30.6 billion/year...
if the open source community was a country with a GDP of $30.6 billion,
it would rank 77 right between Bulgaria and Lithuania...
putting the open source community ahead of most countries in the world...
Such an economic force should not be underestimated, and this is
yet another indication that open source has become a significant part
[of] the technology world."
The specific number may be significantly off, no one knows,
but I think the conclusion (OSS has become a significant part) is spot-on.